The present invention relates generally to interconnection devices and more particularly to interconnection devices for mounting high-frequency multiple millimeter wave assemblies to circuit boards.
Rapid advances in technology have accelerated the need for packaging devices which can accommodate, among other factors, connection requirements, higher operating frequencies and increases in the numbers of inputs and outputs on integrated circuits. Conventional packaging devices include ball grid arrays (BGA), wire bonding, tape automated bonding (TAB), quad flat packs (QFP) and controlled collapse chip connections (C4 or flip chip). BGA packages tend to be particularly popular because they are easier to surface is mount on a printed circuit board than fine pitch peripheral lead packages, such as QFPs. This is because the outer leads of BGA packages are distributed on the lower surface of the package, rather than being restricted to the package perimeter and thus being easier to damage. Moreover, since BGA packages do not include peripheral leads, BGA packages take up less room on a printed circuit board, and may be closely spaced. This close spacing also allows for shorter interconnect lengths between packages, which results in improved electrical performance.
Conventional packaging technologies, including BGA packages, however, fail to address the specific needs of high frequency integrated microwave assemblies (IMAs), particularly with respect to providing low loss, reproducible electrical interconnections at the circuit board level for mounting high frequency IMAs. Specifically, known packaging techniques fail to provide the interconnections which would allow high frequency signal generation, signal reception and digital processing to be combined in a compact space, such as a single circuit board. Rather, separate high frequency coaxial connectors are required to interface the high frequency IMAs with the circuit board.
In high frequency IMAs, arrays of coaxial lines extending from IMA modules must be interconnected to the circuit board. Coaxial transmission lines, commonly employed for the propagation of microwave power in IMAs, include a cylindrical center conductor disposed within a cylindrical tubular outer conductor. Although more costly than open-wire transmission lines, coaxial lines completely enclose the electromagnetic fields, preventing radiation losses and providing shielding from nearby circuits. With a coaxial connector, signal loss is minimized since almost all of the electric field emanating from the signal conductor remains confined in the dielectric. A coaxial conductor will thus electrically insulate the central signal path from any other signals in the vicinity.
Deficiencies can exist with respect to performance in IMAs, particularly at very high frequencies if such interconnections are not properly accommodated. This is because slight variations in signal path impedance may dramatically impact transmission performance. Furthermore, the high frequency interconnection needs to be inexpensive, allowing its use in the commercial market place.
What is needed therefore is a low loss, economical device for connecting millimeter wave assemblies to coaxial lines on substrate boards which would allow high frequency signal generation, signal reception and digital processing to be combined in a single circuit board.